Methods for recycling cotton and polyester fibers from waste textiles

ABSTRACT

Systems and methods are provided that involve a subcritical water reaction to recycle the cellulose and polyester components of waste cotton and cotton/polyester blend textiles that would otherwise be discarded or disposed of. Specifically, the disclosed methods provide for treatment of the waste textiles to produce advanced materials including cellulose and terephthalic acid (TPA) with a low environmental impact. The cellulose and TPA that are produced are of a high quality allowing for production of regenerated cellulose and regenerated polyethylene terephthalate (PET) suitable for fiber spinning and textile applications.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/695,969 filed on Nov. 26, 2019, which is a continuation ofU.S. patent application Ser. No. 16/246,044 filed on Jan. 11, 2019, nowU.S. Pat. No. 10,501,599 issued on Dec. 10, 2019, which claims thebenefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent ApplicationNo. 62/616,543 filed on Jan. 12, 2018, the entire contents of all ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The presently disclosed subject matter relates to a system and methodfor recycling the components of cotton and polyester from textiles. Thepresently disclosed subject matter further relates to a method ofproducing high quality components of cotton and polyesters enabling theproduction of advanced materials using an environmentally-friendlymethod.

BACKGROUND

In the textile industry, finished apparel and related goods have alimited lifespan. When they have ended their useful life, they typicallyend up in a landfill or waste incineration facility. It is estimatedthat more than 15 million tons of used textile waste is generated eachyear in the United States. Regenerated fibers have become increasinglypopular as a sustainable alternative to natural virgin fibers, such ascotton. In general, textiles for recycling are generated from twoprimary sources, including: (1) pre-consumer sources, such as scrapcreated as a by-product from yarn and fabric manufacture; (2)post-consumer sources, such as garments, vehicle upholstery, householditems, and others. Current textile recycling is fundamentally dividedinto two groups for processing. For natural textiles (such as 100%cotton), materials are shredded or pulled into fibers and then processedinto yarn for re-spinning and prepared for subsequent use in weavingand/or knitting. For polyester-based textiles, garments are shredded andthen granulated and processed into polyester chips. The chips aresubsequently melted and used to create new fibers for use in thepolyester fabrics. However, conventional methods of recycling and/orregenerating textiles are associated with significant drawbacks, such asthe use of expensive and harsh hydrolyzing agents, complex recyclingmethods, waste water discharge, pollution, energy use that renders theprocess cumbersome, and significant expenditures of time. It wouldtherefore be beneficial to overcome the shortcomings of currenttechnology by providing a simple and cost-effective method ofregenerating premium recycled fibers that significantly reduces chemicalusage and waste water production.

SUMMARY

In some embodiments, the presently disclosed subject matter is directedto a method of producing one or both of cellulose and terephthalic acid(TPA) from waste textile material comprising essentially 100% cotton orcotton/polyester blend material. Particularly, the method comprisestreating the waste textile material in a subcritical water reactor at atemperature of about 105° C. to 190° C., a pressure of about 40 to 300psi, or both for about 0 to 90 minutes, wherein one or both of acellulose that comprises a degree of polymerization ranging from about150-2500 and a dissolved TPA and ethylene glycol (EG) are produced. Aproduct comprising cellulose with a degree of polymerization of about150-2500 and/or a product comprising a recycled terephthalic acid (TPA)is thereby produced. In some embodiments, the cellulose is furtherrecovered, including by a dissolution process to form regeneratedcellulose.

In some embodiments, the waste textile material comprisescotton/polyester blend material and the treating in the subcriticalwater reactor comprises a pH ranging from about 10-14. The method canfurther comprise recovering the TPA. The method can further compriserecovering the cellulose. The method can further comprise subjecting therecovered cellulose to a disintegration process.

In some embodiments, the waste textile material comprisescotton/polyester blend material and the treating in the subcriticalwater reactor comprises a first treating at a pH ranging from about10-14, wherein the TPA is produced, and a second treating of thecellulose that is produced in the first treating at a pH ranging fromabout 2-4, wherein the cellulose that is produced in the second treatingcomprises a degree of polymerization ranging from about 150-2000. Insome embodiments, the cellulose with a degree of polymerization of about150-2500 is of a purity ranging from about 94%-98%. The method canfurther comprise recovering the cellulose produced after the secondtreating, including by subjecting the cellulose to one or more steps ofwash, disintegration, sour wash, activation process, dissolution dope,or wet spinning.

The method allows for reducing the size of cellulose fibers in the wastetextile material, loosening the cellulose fibers from the waste textilematerial, or both.

In some embodiments, the method further comprises sorting the wastetextile material before or after treatment in the subcritical waterreactor. In some embodiments, the sorting is based on color,composition, weight percent cellulose, non-cellulose components, orcombinations thereof.

The method allows for dissolving cellulose fibers present within thewaste textile material.

In some embodiments, the method further comprises a pretreatment stepreducing the size of the waste textile material. The pretreatment stepcan be by mechanical cutting. In some embodiments, the reducinggenerates a particle size of about 60 mm or less.

In some embodiments, the method further comprises removing color fromthe waste textile material before, during, or after treating with thesubcritical water reactor. In some embodiments, the color removalcomprises treatment with one or more of hydrogen peroxide, sodiumperoxide, sodium hypochlorite, calcium hypochlorite, dimethyl sulfoxide,lithium hypochlorite, sodium perborate, ozone, oxygen, activated carbon,biochar, sodium carbonate, peracetic acid, potassium permanganate,persulfate, sodium chloride, calcium oxychloride, chloramine, chlorinedioxide, sulfur dioxide, sodium hydrosulfite, or TAED(tetra-acetyl-ethylene-di-amine).

In some embodiments, the subcritical water reactor treatment comprisesone or more of methanol, ethanol, isopropanol, tetra-n-butylphosphoniumbromide (TBPB), or benzyltributylammonium chloride (BTBAC), orco-polymers thereof.

In some embodiments, the ratio of waste textile material to water withinthe subcritical water reactor is about 1:5-1:95.

In some embodiments, the method further comprises subjecting the wastetextile material to acid treatment in the subcritical water reactor. Thecellulose in the waste textile material can then be subjected to amechanical disintegration process. This method can allow for recoveringthe cellulose in the waste textile material to produce regeneratedcellulose.

In some embodiments, the method further comprises adjusting the pH ofwater within the subcritical water reactor before subcritical watertreatment. In some embodiments, the pH is adjusted to about 2-4. In someembodiments, the pH is adjusted to about 10-14. In some embodiments, thepH is adjusted using 0.01-5% (v/v) organic acid, 0.5-20% (w/v) sodiumhydroxide, or 0.5-20% (w/v) potassium hydroxide.

In some embodiments, wherein the waste textile material comprises acotton/polyester blend, the subcritical water reactor functions todecompose the polyester and adjust the degree of polymerization of thecellulose macromolecules.

In some embodiments, the subcritical water reactor enables thedissolution of polyester to terephthalic acid (TPA) and ethylene glycol(EG).

In some embodiments, a method is provided for producing terephthalicacid (TPA) from a polyester waste textile material, the methodcomprising: treating the polyester waste textile material in asubcritical water reactor at a temperature of about 105° C. to 190° C.,a pressure of about 40 to 300 psi, or both for about 0 to 90 minutes,wherein a dissolved TPA and ethylene glycol (EG) is produced. The pH canrange from about 10-14. The method can further comprise precipitatingand recrystallizing the TPA.

In some embodiments, the presently disclosed subject matter is directedto a regenerated cellulose material produced using the disclosed method.In some embodiments, the presently disclosed subject matter is directedto a regenerated polyester material produced using the disclosed method.In some embodiments, the products of regenerated cellulose materialinclude rayon, viscose rayon, lyocell, or cellulose acetate. Theregenerated cellulose and TPA have properties making them suitable forfiber spinning and textile applications. For example, in one embodiment,the regenerated cellulose monofilaments of the present disclosure have atenacity ranging from 1.3 g/den to 1.8 g/den and a strain at break ofabout 10% to 12%.

BRIEF DESCRIPTION OF THE DRAWINGS

The previous summary and the following detailed descriptions are to beread in view of the drawings, which illustrate some (but not all)embodiments of the presently disclosed subject matter.

FIG. 1 is a schematic of one embodiment of a sorting/sizing method thatcan be used in accordance with the presently disclosed subject matter.

FIG. 2 is a schematic of one embodiment of a method for producingregenerated fibers from cotton textiles in accordance with someembodiments of the presently disclosed subject matter. The dashed linesindicate optional processing steps of de-coloration, bleaching, andcellulose fiber activation.

FIG. 3 is a schematic of one embodiment of a method for producingregenerated fibers from polyester textiles in accordance with someembodiments of the presently disclosed subject matter. The dashed lineindicates the optional processing step of de-coloration.

FIG. 4 is a schematic of one embodiment of a method for producingregenerated fibers from polycotton textiles in accordance with someembodiments of the presently disclosed subject matter. The dashed linesindicate the optional processing steps of de-coloration, bleaching, andcellulose fiber activation.

FIG. 5 is a graph illustrating the FT-IR results of cellulose recoveredfrom cotton textile produced in accordance with some embodiments of thepresently disclosed subject matter.

FIG. 6 is a schematic illustrating a method of producing regeneratedcellulose filaments in accordance with some embodiments of the presentlydisclosed subject matter.

FIG. 7A is a microscopy image of a single regenerated cellulose filamentproduced in accordance with the presently disclosed subject matter.

FIG. 7B is a microscopy cross-sectional image of a bundle of regeneratedcellulose filament produced in accordance with the presently disclosedsubject matter.

FIG. 7C is a microscopy image of a regenerated cellulose multifilamentknitting sample produced in accordance with the presently disclosedsubject matter.

FIG. 8 is a graph illustrating FT-IR results from precipitated TPArecovered from polycotton textile produced in accordance with someembodiments of the presently disclosed subject matter.

FIG. 9A is an NMR analysis of crystallized TPA from a waterrecrystallization step produced in accordance with some embodiments ofthe presently disclosed subject matter.

FIG. 9B is an NMR analysis of precipitated TPA powder from polycottonfabrics produced in accordance with some embodiments of the presentlydisclosed subject matter.

FIG. 9C is an NMR analysis of crystallized TPA from a waterrecrystallization step produced in accordance with some embodiments ofthe presently disclosed subject matter.

FIG. 10A is a Differential Scanning calorimetry (DSC) of regenerated PETchip produced from 100% recycled terephthalic acid (reTPA) produced inaccordance with some embodiments of the presently disclosed subjectmatter.

FIG. 10B is a Thermogravimetric Analysis (TGA) of regenerated PET chipproduced from 100% recycled terephthalic acid (reTPA) produced inaccordance with some embodiments of the presently disclosed subjectmatter.

DETAILED DESCRIPTION

The presently disclosed subject matter is introduced with sufficientdetails to provide an understanding of one or more particularembodiments of broader inventive subject matters. The descriptionsexpound upon and exemplify features of those embodiments withoutlimiting the inventive subject matters to the explicitly describedembodiments and features. Considerations in view of these descriptionswill likely give rise to additional and similar embodiments and featureswithout departing from the scope of the presently disclosed subjectmatter.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood to one of ordinary skill inthe art to which the presently disclosed subject matter pertains.Although any methods, devices, and materials similar or equivalent tothose described herein can be used in the practice or testing of thepresently disclosed subject matter, representative methods, devices, andmaterials are now described.

Following long-standing patent law convention, the terms “a”, “an”, and“the” refer to “one or more” when used in the subject specification,including the claims. Thus, for example, reference to “a reactor” caninclude a plurality of such reactors, and so forth.

Unless otherwise indicated, all numbers expressing quantities ofcomponents, conditions, and so forth used in the specification andclaims are to be understood as being modified in all instances by theterm “about”. Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the instant specification and attachedclaims are approximations that can vary depending upon the desiredproperties sought to be obtained by the presently disclosed subjectmatter.

As used herein, the term “about”, when referring to a value or to anamount of mass, weight, time, volume, concentration, and/or percentagecan encompass variations of, in some embodiments +/−20%, in someembodiments +/−10%, in some embodiments +/−5%, in some embodiments+/−1%, in some embodiments +/−0.5%, and in some embodiments +/−0.1%,from the specified amount, as such variations are appropriate in thedisclosed methods.

The presently disclosed subject matter is directed to a system andmethod of processing cellulose-comprising materials,polyester-comprising materials, and/or polycotton(polyester-cotton)-comprising materials, such as pre-consumer orpost-consumer textiles, fabric scraps, and other materials that wouldotherwise be discarded or disposed of. Specifically, the disclosedsystem and method provides for treatment of textiles that includecellulose, polyester, and/or cellulose blended with polyester.Regenerated cellulose and PET filaments are produced from the wastetextile materials according to the methods of the present disclosure.The terms “regenerated” and “recycled” are herein used interchangeablyfor the purposes of the specification and claims. Implementation of thedisclosed system and method can produce regenerated fibers and textileproducts with improved properties using processes with low environmentalimpacts. For example, in one embodiment, the regenerated cellulosemonofilaments of the present disclosure have a tenacity ranging from 1.3g/den to 1.8 g/den and a strain at break of about 10% to 12%.

In the presently disclosed system and method, any material thatcomprises cellulose, polyester, and/or polycotton can be used as thestarting material. For example, in some embodiments, the startingmaterial can be a waste cotton and/or waste polycotton (cotton/polyesterblend) material found in post-consumer waste textiles and othercellulose-containing fabrics (towels, bedding, upholstery, etc.). Forthe purposes of the specification and claims, the terms “polycotton” and“cotton/polyester blend” are herein used interchangeably. Cotton fiberis the only natural pure cellulose, with a cellulose content of up toabout 95-97 weight percent. The term “cellulose” as used herein refersto a polysaccharide having the formula (C₆H₁₀O₅)_(n) configured as alinear chain of β(1→4) linked D-glucose units (cellobiose), asillustrated in Structure (I), below:

The individual glucose monomers in the cellulose polymer are oftenreferred to as anhydroglucose units (or “AGU”). The number of AGU unitsdefines as the “Degree of Polymerization” (DP) of the cellulose. In thepresently disclosed system and method, viscosity measurements can beused to assess changes in the DP of cellulose in cellulosic pulp aftersubcritical water treatment. For the purposes of the specification andclaims, the terms “cellulosic pulp”, “pulp”, “cotton pulp”, and “cottonsheet” are herein used interchangeably, and refer to the cellulose thatis produced from the waste textile fabric by the subcritical watertreatment of the present disclosure. The cellulose viscosity (unit inmPa·s) is determined according to TAPPI T230 om-94 (1994) (incorporatedherein by reference) in cupriethylenediamine (CED) solution. Theintrinsic viscosity [η] (unit in ml/g) can be calculated from Equation 1below (Mazumder B. B. et al. 2000, Journal of Wood Science 46(5),364-370):

[η]=954×lg (viscosity)−325  Equation 1:

The average DP can be calculated from the intrinsic viscosity usingEquations 2 (Sihtola et al. 1963; Paper Ja Puu 45, 225-232) and 3,below:

DP^(0.905)=0.75×[η]  Equation 2:

DP=k×[η]; K=1.9  Equation 3:

In the presently disclosed system and method, the subcriticalwater-treated textile cellulosic pulp can have a viscosity range ofabout 3 mPa·s to about 55 mPa·s, which refers to a DP of about 150-2500,such as about 200-2000, 300-1700, 400-1500, 500-1200, 600-1000, or700-800. Thus, the treated cellulosic pulp can have a DP of at leastabout (or no more than about) 150, 200, 300, 400, 500, 600, 700, 800,900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000,2100, 2200, 2300, 2400, or 2500.

Polyesters are a group of polymers commonly used in textileapplications. The polymer is a very large molecule build up from smallermolecules. The most common type of polyester used in textiles ispolyethylene terephthalate (PET) (Structure II, below), which cancombine with cotton fiber to form polycotton.

The term “textile” is broadly used herein, and includes fibers,filaments, yarns, woven and non-woven fabrics, knits, and finishedproducts (such as garments).

As set forth in FIG. 1, the disclosed system comprises a sortingcomponent where the waste textiles are sorted according to one or moredesired parameters. For example, in some embodiments, the waste textilescan be sorted according to composition, such as to separate 100% cottonmaterials from cotton/polyester blends and the like. In someembodiments, the textiles can be sorted according to cellulose content(e.g., >90%, >80%, >70%, >60%, >50% or <50% cellulose). In someembodiments, the textiles can be sorted to separate out non-cellulosicmaterial, such as zippers, tags, buttons, and the like. In someembodiments, the textiles can be sorted according to color. The sortingstep can be accomplished using any known mechanical sorting device orcan be done by hand.

In some embodiments, the methods of the present disclosure comprise amechanical cutting device that is configured to reduce the textile sizeand/or to provide a more uniform textile size prior to furthertreatment. Typically, textile materials that include cotton, fabric,yarn, and fibers have a fiber length of greater than 5 mm to 100 mm. Insome embodiments, the cutting device reduces the fiber length to about60 mm or less. The cutting device can include any device capable oftrimming textile size, such as (but not limited to) one or more blades,needles, shredders, pullers, grinders, cutters, rippers, and the like.In some embodiments, the waste textiles are cut to a size of about 5-60mm in length and/or width. However, the presently disclosed subjectmatter is not limited, and the waste materials can be cut into anydesired size. Advantageously, reducing the size of the cellulosictextile material increases the surface area for further treatment (e.g.,subcritical water treatment).

In some embodiments, the sorting process can be conducted by manualplatform or any known current waste textile automation recycling machineto separate the materials into three streams, as shown in FIGS. 2, 3,and 4. Particularly, stream 1 can comprise essentially 100% cotton,stream 2 can comprise essentially 100% polyester, and stream 3 cancomprise polycotton (cotton and polyester in any ratio). In someembodiments, the sorting process can initially scan using an opticalsensor to separate the waste textiles by color. The materials can thenbe scattered thoroughly by a uniform distributing machine.Non-cellulosic materials (such as zippers, tags, buttons, and the like)can then be removed. The sorting and sizing steps can optionally berepeated to enhance the efficiency of the disclosed fiber regenerationprocess.

The methods of the present disclosure comprise a subcritical waterreactor. Particularly, the waste textiles are introduced to the reactorfor treatment with subcritical water to weaken the linkage between thefibers in the textiles. The subcritical water reactor further functionsto decompose the polyester and adjust the degree of polymerization ofthe cellulose macromolecules. In addition, the subcritical water reactorenables the dissolution of polyester to terephthalic acid (TPA) andethylene glycol.

The term “reactor” as used herein refers to a device that can be usedfor any number of chemical processes involving a starting material. Insome embodiments, the reactor comprises a hydrothermal reactor. The term“hydrothermal” as used herein refers to an aqueous system under pressureand increased temperature, typically near or below the critical point ofwater (374° C., 22.1 MPa). Thus, the reactor can provide hydrothermalconditions, such as (but not limited to) a batch reactor,semi-continuous, or continuous reactor. In some embodiments, a batchreactor is preferred. The term “subcritical water” as used herein refersto liquid water at temperatures between the atmospheric boiling point(100° C.) and the critical temperature (374° C.) that present uniquefeatures with respect to its properties, such as density, dielectricconstant, ion concentration, diffusivity, and solubility. In thesubcritical region, the ionization constant (Kw) of water increases withtemperature and is about three orders of magnitude higher than that ofambient water, and the dielectric constant of water drops from 80 to 20.

Advantageously, subcritical water is a non-toxic, environmentallybenign, inexpensive, and green solvent that can be used as analternative to harsh chemicals traditionally used in the fabricrecycling industry. In the disclosed method and the system, the use ofsubcritical water hydrothermal treatment allows higher diffusion,activity, and ionization of water. In some embodiments, the partialhydrolysis of cellulose and the breakdown of the cross-link between thecotton cellulose and polyester in the textile can be achieved.

In some embodiments, adjustable hydrothermal reaction conditions can beapplied to produce cellulose in a broad desired DP range (DP: 150-2500)that can be used to manufacture a wide variety of regenerated celluloseproducts, such as rayon, viscose rayon, lyocell, lyocell-like, orcellulose acetate. In some embodiments, the subcritical water reactorcan mix with one or more co-solvents (e.g., methanol, ethanol,isopropanol) such that a temperature of about 105° C. to 190° C. (e.g.,about 105-190, 110-180, 120-175, 130-160, 140-150, 140-170, 150-160,160-190, 170-180, 165-190, or 175-185° C.) and/or a pressure of about 40to 300 psi (e.g., about 40-300, 60-280, 80-250, 80-120, 110-140,120-150, or 100-250 psi) can be achieved for residence time about 0 to90 minutes (e.g., about 0-90, 10-80, 20-70, 30-60, 40-70, or 40-50minutes). In some embodiments, the co-solvents can be present in anamount of from about 0-100 weight percent, such as about 1-90, 5-80,10-70, 20-60, or 30-50 weight percent.

In some embodiments, the disclosed method can include a phase transfercatalyst (PTC) to improve the process efficiency and to reduce energyconsumption. The term “phase transfer catalyst” refers to any agentcapable of facilitating a reactor by virtue of the ability to dissolveas ion pairs in both aqueous and organic solvents. Any desired PTC canbe used, such as (but not limited to) any commercially availableammonium or phosphonium-based PTC, such as tetra-n-butylphosphoniumbromide (TBPB), benzyltributylammonium chloride (BTBAC), or co-polymersetc.

The waste textiles can be transferred to the reactor and processed for adesired amount of time. In some embodiments, the textiles can be treatedin the reactor at a temperature of about 105° C. to 190° C., at apressure of about 40 to 300 psi, or both. In some embodiments, the ratioof textile material to water is about 1:5-1:95 (e.g., 1:5, 1:10, 1:11,1:12, 1:13, 1:14, 1:15, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:30, 1:31,1:32, 1:33, 1:34, 1:35, 1:40, 1:45, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75,1:80, 1:81, 1:82, 1:83, 1:84, 1:85, 1:86, 1:87, 1:88, 1:89, 1:90, 1:91,1:92, 1:93, 1:94, 1:95). In some embodiments, the reaction time can beabout 0-90 minutes, such as at least about (or no more than about) 0, 5,10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90minutes.

In the reactor, the linkage between the fibers in the textiles isweakened as a result of the temperature and/or pressure. Particularly,the high temperature and/or pressure of the subcritical water promotesmolecular separation of the cellulose polymers and deconstructsintermolecular hydrogen bonds and other non-covalent bonds within thewaste textiles. As a result, the cellulose-containing textiles areconverted to their constituent cellulose polymers. In some embodiments,the number of intermolecular hydrogen bonds in the cellulosic materialis reduced by at least 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% afterthe subcritical water treatment. Thus, treatment with subcritical waterprovides an environmentally-friendly way to break down the cellulose inthe waste textile materials.

In some embodiments, the pH of the starting material (e.g., water andtextile mixture) in the reactor can be adjusted to enhance subcriticalwater reaction efficiency. For example, 0.01%-2% acetic acid can be usedwith cotton textile to adjust the pH to about 4. In some embodiments,the pH can be adjusted to a range of about 2 to 4 for cotton textile.For cotton/polyester textile blends, 0.01%-5% acetic acid can be used togenerate a pH of 2-4. In embodiments where the textile comprisescotton/polyester blends and/or polyester, 0.5-20% sodium hydroxide(NaOH) or potassium hydroxide (KOH) can be used to achieve a pH of about10-14. In some embodiments, polyester (PET) textile can be degraded viahydrolysis using 0.5-20% NaOH, and can further be dissolved through asubcritical water treatment. However, it should be appreciated that theacid/base is not limited, and any suitable acid or base can be used toadjust the pH to a desired level. In some embodiments, the KOH, NaOH,acetic acid, and/or other organic acids function as a reagent toincrease the rate of the reaction.

As illustrated in FIG. 2 and described in EXAMPLES 1 through 4, inembodiments wherein the starting textile material is essentially 100%cotton textile (e.g., shredded textile material), the disclosed methodincludes depositing the material in a subcritical water reactor (e.g.,Condition I, an appropriate pH, e.g. pH 2-pH 6 or pH 2-4 and temperatureadjustment, 105° C.-190° C.).

In one embodiment, the cellulose resulting from the subcritical waterreaction is washed and subjected to a disintegration process to loosenthe cellulose fibers as described in EXAMPLES 1 through 4. In thismanner the cellulose can be further processed for dissolution. In someembodiments, after this treatment, the disintegrated fibers aresubjected to a sour wash pulp process, which entails a treatment withdilute aqueous sulfur dioxide solution using industry standardconditions. A cellulose fiber activation process may be initiated whenutilizing certain dissolution systems. This involves producing a groundcellulose pulp sample in aqueous NaOH solution (e.g., 12-15% w/v), 1:20(cellulose sample:aqueous solution), stirring at room temperature for3-4 hours, washing to neutral pH, drying, subjecting to an acidtreatment (e.g., with 1M sulfuric acid for 45-60 minutes), washing toneutral pH, and air drying. Cellulose dissolute dope can then beprepared by incorporating a dissolving component. The cellulose can bedissolved with molten organic salts (e.g., ionic liquids), such asN-alkylpyridium salts and similar agents, amine oxides (such asN-methylmorpholine-N-oxides and similar agents), and/or polar andaprotic liquids (such as N, N-dimethylacetamide/LiCl and similar agents)to provide a dissolved cellulose suitable for regenerated fiberproduction utilizing industrial standard techniques.

As illustrated in FIG. 3 and described in EXAMPLE 5, in embodimentswherein the starting textile material is essentially 100% polyestertextile (e.g., cut textile material), the disclosed method includesdepositing the material in a subcritical water reactor (e.g., Condition2, at an appropriate pH (e.g. pH 10-14) and with a temperatureadjustment (105° C.-190° C.). After treatment, the processed solutioncan be removed and terephthalic acid (TPA) formed by precipitation byadjusting the pH (e.g., to pH 2-6). The TPA can then be carried forwardto crystallization. This entails heating an aqueous solution withprecipitated TPA to a temperature of about 250° C. to 300° C., a ratioof solid:water of about 1:4 to 1:10, with a residence time of about 0 to10 minutes (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 minutes). Thecrystalized TPA can then be subjected to a PET polymerization process toproduce regenerated PET. This process can involve treating thecrystallized TPA with ethylene glycol in an industry standard batchautoclave at temperatures between 235° C.-290° C. with appropriatecatalyst (e.g. antimony or titanium catalyst packages). Additionally,ethylene glycol can be recovered from the processed solution usingindustry standard techniques (e.g. vacuum distillation).

As illustrated in FIG. 4 and described in EXAMPLES 6 through 9, inembodiments where the starting textile material includescotton/polyester blends, the subcritical water treatment (e.g.,Condition II, an appropriate pH (e.g. pH 10-pH14) and temperatureadjustment (e.g., 105° C.-190° C.)) can be effective to separate thecotton from the dissolved polyester monomers; TPA and ethylene glycol.Particularly, the subcritical water treatment produces liquefiedpolyester monomers, and cellulose. After treatment, the processedsolution is removed and TPA is formed by precipitation using anappropriate pH adjustment (e.g., pH 2-6). The TPA can then be carriedforward to crystallization, which entails heating an aqueous solutionwith precipitated TPA to a temperature of about 250° C. to 300° C., aratio of solid:water of about 1:4 to 1:10, with a residence time ofabout 0 to about 10 minutes (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10minutes). The crystalized TPA can then be subjected to a PETpolymerization process to produce regenerated PET. This process caninvolve treating the crystallized TPA with ethylene glycol in anindustry standard batch autoclave at temperatures between 235° C.-290°C. with an appropriate catalyst (e.g. antimony or titanium catalystpackages). Additionally, ethylene glycol can be recovered from theprocessed solution using industry standard techniques (e.g. vacuumdistillation).

The waste textiles can be partially or fully treated to remove coloring(e.g., pigments, dyes, etc.) and/or to improve brightness throughout thesubcritical water hydrothermal process by adding about 0.5-20% NaOH. Anyconventional de-coloration/dye removal element can be used. For example,in some embodiments, the de-coloration/dye removal element can beselected from one or more of hydrogen peroxide, sodium peroxide, sodiumhypochlorite, calcium hypochlorite, dimethyl sulfoxide, lithiumhypochlorite, sodium perborate, activated carbon powder, biochar, ozone,oxygen, sodium carbonate, peracetic acid, potassium permanganate,persulfate, sodium chloride, calcium oxychloride, chloramine, sulfurdioxide, sodium hydrosulfite, or TAED (tetra-acetyl-ethylene-di-amine).

Further, the disclosed system can comprise a disintegration component.Specifically, after subcritical water reaction, the cellulose can berecovered and subjected to a disintegration component where thecellulose fibers are loosened from the textile pulp as shown in FIG. 4.Any conventional disintegration method can be used, such as (but notlimited to) ultrasound, homogenization, and/or grinding.

Further, the disclosed system can comprise a dissolving componentwherein the cellulose is dissolved by molten organic salts (e.g., ionicliquids), such as N-alkylpyridium salts and similar agents, amine oxides(such as N-methylmorpholine-N-oxides and similar agents), and/or polarand aprotic liquids (such as N, N-dimethylacetamide/LiCl and similaragents). In some embodiments, the dissolving component can include oneor more additives at a concentration of about 0.1% to 15 weight % (e.g.,0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 weight%). The additives can promote the production of regenerated cellulosefilaments with enhanced mechanical properties (such as higher tenacityand elongation additives). Suitable additives can include (but are notlimited to) glyceric acid, gluconic acid, glucuronic acid, galacturonicacid, iduronic acid, mucic acid, and/or glucaric acid. In someembodiments, the dissolving component can comprise powdered titaniumdioxide (e.g., 0.1-10 weight %) to produce semi-dull or dull filaments.

After the disintegration of the cellulose fibers, the isolated cellulosemolecules can be used to form regenerated cellulose fibers and textilematerials. In some embodiments, “regenerated cellulose” refers tocellulose that has been prepared by regeneration (i.e., returned tosolid form) from a solution that includes dissolved cellulose fibers. Insome embodiments, the isolated cellulose molecules can be dissolved bymolten organic salts (e.g., ionic liquids), such as N-alkylpyridiumsalts and similar agents, amine oxides (such asN-methylmorpholine-N-oxides and similar agents), and/or polar andaprotic liquids (such as N, N-dimethylacetamide/LiCl and similaragents), and spun in a coagulation bath to produce regeneratedcellulosic fibers, such as rayon, viscose rayon, lyocell, lyocell-like,or cellulose acetate. The newly formed fibers can be stretched and/orblown to a desired configuration, washed, dried, and cut to a desiredlength. The regenerated cellulosic fibers can be twisted into thread,dyed, bleached, woven into textiles, and ultimately can be cut and sewninto garments. Thus, the treated fabric can be used to manufacture agarment such as (but not limited to) shirts, pants, hats, coats,jackets, shoes, socks, uniforms, athletic clothing, and swimwear. It isalso possible and contemplated that the treated fabric can be used toconstruct non-apparel items, such as blankets, sheets, sleeping bags,backpacks, tents, insulation materials, and the like.

Thus, in use, the disclosed system can be used to recycle one or both ofcellulose and terephthalic acid (TPA) and ethylene glycol (EG) from anystarting textile material comprising cellulose, polyester, and/orpolycotton. The recycled cellulose can be used to produce regeneratedcellulose and the recycled terephthalic acid (TPA) and ethylene glycol(EG) can be used to produce regenerated PET. Particularly, the wastetextiles can be provided and sorted based on desired parameters (e.g.,percentage cellulose, composition, color, and the like). The sortedtextiles can be exposed to a cutting device, blending device, or both toensure that the textile material is of a suitable size and uniform sizefor treatment. The cut and/or blended textile material can be optionallybleached to remove or decrease the amount of dyes, finishes, and/orcontaminants. The textile material is introduced to a reactor where asubcritical water reaction is performed for a temperature, pressure, andtime sufficient to dissolve PET and weaken the linkage between thecellulose fibers (e.g., Condition II, an appropriate pH, e.g., pH 10-pH14, and temperature adjustment, e.g., 105° C.-190° C.). Dissolved TPAthen can be precipitated through pH adjustment, filtered under vacuum,and washed to neutral condition. The washed TPA can be dried and carriedforward to crystallization. Crystalized TPA can be subjected to a PETrepolymerization process to produce regenerated PET. The cottoncellulose material can be recovered. In some embodiments, the recoveredcellulose materials can be disintegrated and can be used to produceregenerated cellulose fibers. In some embodiments, the recoveredcellulose material can be disintegrated as staple fiber to blend witheither virgin cotton fibers or other fibers as recycled cotton blendyarn. In some embodiments, the recovered cellulose material can bewashed and cut into in smaller pieces. The pieces can have an averagesize ranging from about 4-6 mm. The pieces can be subjected to a secondsubcritical water treatment (e.g., Condition I, an appropriate pH, e.g.,pH 2-pH 4, and temperature adjustment, e.g., 105° C.-190° C.) such asdescribed in EXAMPLES 6 through 8. Subcritical water treated wastetextiles can be exposed to a disintegration component where thecellulose fibers are loosened from the pulp material such as describedin Example 10. The recovered cellulose is then exposed to a dissolvingcomponent to promote dissolving of the cellulose. After the dissolvingof the cellulose fibers, the isolated cellulose molecules can be used toform regenerated cellulose fibers and textile materials.

FIG. 5 shows the results of Fourier Transform Infrared testing verifyingthat cellulose was recovered from the waste cotton textile treatedaccording to the methods of the present disclosure. The purity of therecovered cellulose can range from about 94%-98% (as calculated by HPLCanalysis). Cellulose dope can be used to produce continuous regeneratedcellulose filament and textile products, as set forth in the schematicof FIG. 6. The cellulose monofilament produced according to the methodsof the present disclosure can have a tenacity ranging from about 1.3g/den to 1.8 g/den and a strain at break of about 10% to 12%. Opticalmicroscopy images of regenerated cellulose filaments produced accordingto the methods of the present disclosure are shown in FIGS. 7a-7c .Particularly, FIG. 7a illustrates microscopy images (4×) of aregenerated cellulose filament. FIG. 7b is a cross-sectional microscopyimage (4×) of a bundle filament, wherein the cross-section of eachindividual filament indicates an oval-alike shape. FIG. 7c is a confocalmicroscopy image (2×) of a knitting sample, depicting multi-filaments.

EXAMPLE 11 describes the physical properties of the regeneratedpolyester produced from waste polycotton textiles according to themethods of the present disclosure. As described herein, polycottontextiles are subjected to subcritical water treatment such as, forexample, condition II as described in Example 6, and the resulting TPAcarried forward to crystallization and PET polymerization to produceregenerated PET. An FT-IR analysis of the resulting TPA is shown in FIG.8. NMR analysis of the TPA from water recrystallization is shown in FIG.9a . Precipitated TPA powder from the polycotton fabrics (zoomed at thealiphatic region) is shown before (FIG. 9b ) and after recrystallization(FIG. 9c ). FIGS. 9a-9c illustrate the reduction in impurities afterrecrystallization. Differential Scanning calorimetry (DSC) ofregenerated PET chip produced from 100% recycled TPA according to themethods of the present disclosure is shown in FIG. 10a . As shown, ThePET reference standard peak temperature is 246.139° C., and thedisclosed method produced regenerated PET with a peak temperature of251.800° C. The thermogravimetric analysis (TGA) of regenerated PET chipproduced from 100% recycled TPA is shown in FIG. 10b . As shown, the PETreference standard had an onset x=425.33° C., and the disclosed methodproduced regenerated PET with an onset x=426.040° C.

EXAMPLES

The following Examples have been included to provide guidance to one ofordinary skill in the art for practicing representative embodiments ofthe presently disclosed subject matter. In light of the presentdisclosure and the general level of skill in the art, those of skill canappreciate that the following Examples are intended to be exemplary onlyand that numerous changes, modifications, and alterations can beemployed without departing from the scope of the presently disclosedsubject matter.

Example 1 Recycling Cotton Textiles Using Treatment with SubcriticalWater for Adjusting Degree of Polymerization within the Cellulosic Pulp

The method set forth in FIG. 2 can be used to recycle cotton textiles.Particularly, a sample of essentially 100% cotton waste textiles wasobtained and cut into pieces, average size 5 mm. The textile pieces wereintroduced into a hydrothermal reactor (Parr 4553M 2-gallon reactor,available from Parr Instrument Company, Moline, Ill.) for subcriticalwater treatment (“Condition I”). The reactor temperature 175° C., aceticacid concentration of about 0.05%-0.1% (v/v), once the desiredtemperature was attained, residence time was 60 minutes, and pressureranged from 80-120 psi. The solid:water ratio was 1:88. During thesubcritical water reaction, the linkages between the fibers inside thetextiles were weakened.

After subcritical water treatment, a disintegration process wasperformed using a standard fiber disintegrator at 2-3% cellulosic pulpconcentration for 10 minutes operation time to loosen the fiber bindingand to produce disintegrated cellulose. The resulting cellulosic pulpproduct had a viscosity of 3.2 mPa·s, which was calculated based fromEquations 1, 2, 3 as about DP 240-370. The disintegrated cellulose wassubjected to a separation process to recover the cellulose fiber.

Fourier Transform Infrared (FT-IR; Jasco 6200 with Pike MIRacle ATRattachment. Range: 4000-600 cm⁻¹, Number of scans: 128) testing wasconducted to verify the presence and the type of polymer produced. Asshown in FIG. 5, the results indicate cellulose was recovered from thewaste cotton textile.

Example 2 Recycling Cotton Textiles Using Treatment with SubcriticalWater for Adjusting Degree of Polymerization within the Cellulosic Pulp

The method set forth in FIG. 2 can be used to recycle cotton textiles.Particularly, a sample of essentially 100% cotton waste textiles wasobtained and cut into pieces, average size 5 mm. The textile pieces wereintroduced into a hydrothermal reactor (Parr 4553M 2-gallon reactor,available from Parr Instrument Company, Moline, Ill.) for subcriticalwater treatment (“Condition I”). The reactor temperature 155° C., aceticacid concentration of about 0.05%-0.1% (v/v), once the desiredtemperature was attained, residence time was 60 minutes, and pressureranged from 80-120 psi. The solid:water ratio was 1:94. During thesubcritical water reaction, the linkages between the fibers inside thetextiles were weakened. The resulting cellulosic pulp product had aviscosity of 4.9 mPa·s, which was then calculated based from Equations1, 2, 3 as about DP 450-640.

After subcritical water treatment, a disintegration process wasperformed using a standard fiber disintegrator at 2-3% cellulosic pulpconcentration for 10 minutes operation time to loosen the fiber bindingand to produce disintegrated cellulose. The disintegrated cellulose wasthen subjected to a separation process to recover the cellulose fiber.

Example 3 Recycling Cotton Textiles Using Treatment with SubcriticalWater for Adjusting Degree of Polymerization within the Cellulosic Pulp

The method set forth in FIG. 2 can be used to recycle cotton textiles.Particularly, a sample of essentially 100% cotton waste textiles wasobtained and cut into pieces, average size 5 mm. The textile pieces wereintroduced into a hydrothermal reactor (Parr 4553M 2-gallon reactor,available from Parr Instrument Company, Moline, Ill.) for subcriticalwater treatment (“Condition I”). The reactor temperature 155° C., aceticacid concentration of about 0.05%-0.1% (v/v), once the desiredtemperature was attained, residence time was 0 minutes, and pressureranged from 80-120 psi. The solid:water ratio was 1:31. During thesubcritical water reaction, the linkages between the fibers inside thetextiles were weakened. The resulting cellulosic pulp product had aviscosity of 16.8 mPa·s, which was then calculated based from Equations1, 2, 3 as about DP 1200-1600.

After subcritical water treatment, a disintegration process wasperformed using a standard fiber disintegrator at 2-3% cellulosic pulpconcentration for 10 minutes operation time to loosen the fiber bindingand to produce disintegrated cellulose. The disintegrated cellulose wasthen subjected to a separation process to recover the cellulose fiber.

Example 4 Recycling Cotton Textiles Using Treatment with SubcriticalWater for Adjusting Degree of Polymerization within the Cellulosic Pulp

The method set forth in FIG. 2 can be used to recycle cotton textiles.Particularly, a sample of essentially 100% cotton waste textiles wasobtained and cut into pieces, average size 5 mm. The textile pieces wereintroduced into a hydrothermal reactor (Parr 4553M 2-gallon reactor,available from Parr Instrument Company, Moline, Ill.) for subcriticalwater treatment (“Condition I”). The reactor temperature 155° C., aceticacid concentration of about 0.05%-0.1% (v/v), once the desiredtemperature was attained, residence time was 0 minutes, and pressureranged from 80-120 psi. The solid:water ratio was 1:21. During thesubcritical water reaction, the linkages between the fibers inside thetextiles were weakened. The resulting cellulosic pulp product had aviscosity of 27.9 mPa·s, which was then calculated based from Equations1, 2, 3 as about DP 1600-2000.

After subcritical water treatment, a disintegration process wasperformed using a standard fiber disintegrator at 2-3% cellulosic pulpconcentration for 10 minutes operation time to loosen the fiber bindingand to produce disintegrated cellulose. The disintegrated cellulose wasthen subjected to a separation process to recover the cellulose fiber.

Example 5 Recycling 100% Polyester Textiles Using Subcritical WaterTreatment

The method set forth in FIG. 3 can be used to recycle polyestertextiles. Particularly, a sample of essentially 100% polyester wastetextiles was obtained and cut into pieces (30 cm×30 cm). The textilepieces were introduced into a hydrothermal reactor (Parr 4553M 2-gallonreactor, available from Parr Instrument Company, Moline, Ill.) forsubcritical water treatment (“Condition II”). The reactor temperaturewas about 175° C.-180° C., with sodium hydroxide about 5% (w/v),residence time was 60 minutes, and pressure ranged from 110-140 psi. Thesolid/water ratio was about 1:5. After treatment, the processed solutionwas removed and TPA was formed by precipitation using a pH adjustment(e.g. pH 2-pH 4). The precipitated TPA was then carried forward tocrystallization. This entailed heating an aqueous solution withprecipitated TPA to a temperature of about 250° C. to 300° C., a ratioof solid:water of about 1:5, with a residence time of about 5 minutes.The crystalized TPA was then treated with ethylene glycol in batchautoclave at temperatures about 290° C. with Antimony metal (5b203) ascatalyst for a PET polymerization process to produce regenerated PETwith a target intrinsic viscosity (IV) of 0.620 dl/g.

Example 6 Recycling Polycotton Textiles Using Treatment with SubcriticalWater for Adjusting Degree of Polymerization within the Cellulosic Pulp

The method set forth in FIG. 4 can be used to recycle polycottontextiles.

Particularly, a sample of 80/20 polycotton (polyester:cotton=80:20)waste textiles was obtained and cut into sheets, average size 30 by 30cm. The textile sheets were introduced into a hydrothermal reactor (Parr4553M 2-gallon reactor, available from Parr Instrument Company, Moline,Ill.) for subcritical water treatment (“Condition II”). The reactortemperature 180° C., with sodium hydroxide about 5% (w/v), residencetime was 60 minutes, and pressure ranged from 120-150 psi. Thesolid/water ratio was 1:11. After treatment, the dissolved TPA wasrecovered, and the method described above in Example 5 was used toproduce regenerated PET.

In addition to the TPA, the cellulose that was produced in thesubcritical water treatment was also recovered. During the subcriticalwater reaction, the linkages between the fibers inside the textiles wereweakened, and the resulting cellulosic pulp product had a viscosity of 6mPa·s (calculated as DP 600-800). The pulp was then washed and cut intopieces, with an average size of about 5 mm. The textile pieces wereintroduced into a hydrothermal reactor (Parr 4553M 2-gallon reactor,available from Parr Instrument Company, Moline, Ill.) for subcriticalwater treatment (“Condition I”). After subcritical water treatment, theproduct was washed and subjected to a disintegration process at 2-3%cellulosic pulp concentration for 10 minutes operation time to loosenthe fiber binding. The disintegrated fibers were subjected to aseparation process to recover the cellulose fiber. The resultingcellulosic pulp product had a viscosity of 4 mPa·s (calculated as DP300-500).

Example 7 Recycling Polycotton Textiles Using Treatment with SubcriticalWater and Phase Transfer Catalyst for Adjusting Degree of Polymerizationwithin the Cellulosic Pulp

The method set forth in FIG. 4 can be used to recycle polycottontextiles. Particularly, a sample of 80/20 polycotton(polyester:cotton=80:20) waste textiles was obtained and cut intosheets, average size 30 by 30 cm. The textile sheets were introducedinto a hydrothermal reactor (Parr 4553M 2-gallon reactor, available fromParr Instrument Company, Moline, Ill.) for subcritical water treatment(“Condition II”). The reactor temperature 155° C., with sodium hydroxideabout 5% (w/v), 0.5% BTBAC (w/v), residence time was 60 minutes, andpressure ranged from 120-150 psi. The solid/water ratio was 1:10. Aftertreatment, the dissolved TPA was recovered and the method described inExample 5 was used to produce regenerated PET.

For the recovered cellulosic pulp product, during the subcritical waterreaction, the linkages between the fibers inside the textiles wereweakened, and the resulting product had a viscosity about 50.5 mPa·s(calculated as DP 2000-2500). The pulp was then washed and cut intopieces, with an average size of about 5 mm. The pieces were introducedinto a hydrothermal reactor (Parr 4553M 2-gallon reactor, available fromParr Instrument Company, Moline, Ill.) for subcritical water treatment(“Condition I”) to produce cellulosic pulp with a desired viscosity byfollowing the methods of Example 1, 2, 3 and 4.

Example 8 Recycling Polycotton Textiles Using Treatment with SubcriticalWater and Co-Solvent for Adjusting Degree of Polymerization within theCellulosic Pulp

The method set forth in FIG. 4 can be used to recycle polycottontextiles. Particularly, a sample of 80/20 polycotton(polyester:cotton=80:20) waste textiles was obtained and cut intosheets, average size 30 by 30 cm. The textile sheets were introducedinto a hydrothermal reactor (Parr 4553M 2-gallon reactor, available fromParr Instrument Company, Moline, Ill.) for subcritical water treatment(“Condition II”). The reactor temperature 150° C., with sodium hydroxideabout 5% (w/v), 10% MeOH (v/v), residence time was 60 minutes, andpressure ranged from 120-150 psi. The solid/water ratio was 1:10. Aftertreatment, the dissolved TPA was recovered and the method described inExample 5 was used to produce regenerated PET.

For the recovered cellulosic pulp product, during the subcritical waterreaction, the linkages between the fibers inside the textiles wereweakened, and the resulting product had a viscosity about 35 mPa·s(calculated as DP 1750-2200). The pulp was then washed and cut intopieces, with an average size of about 5 mm. The pieces were introducedinto a hydrothermal reactor (Parr 4553M 2-gallon reactor, available fromParr Instrument Company, Moline, Ill.) for subcritical water treatment(“Condition I”) to produce cellulosic pulp with a desired viscosity byfollowing the methods of Example 1, 2, 3 and 4.

Example 9 Recovery of Cotton Fibers from Polycotton Textiles

Polycotton textiles were subjected to the subcritical water treatment(condition II) described in Example 8. After the treatment, the TPA wasdissolved, and the cellulose materials were recovered with a viscosityabout 35 mPa·s (calculated as DP 1750-2200). The cotton sheets were thenshredded and disintegrated for use as staple fibers to blend with virgincotton fibers or other fibers as recycled cotton blend yarn.

Example 10 Regenerated Cellulose Filament Produced from RecyclingPolycotton Textiles

The cellulosic pulp product that resulted from the method of Example 6was subjected to a sour wash process with diluted aqueous sulfur dioxidesolution (pH 2-pH 3), 1:20 (cellulose sample:aqueous solution) andstirred for 1.5 hours at room temperature. The sour washed pulp was thenfiltered, washed with DI water until neutral pH was obtained, and airdried. A cellulose fiber activation process was performed that includedproducing a ground cellulose pulp sample in aqueous NaOH solution (15%w/v), 1:20 (cellulose sample:aqueous solution), stirring for 4 hrs atroom temperature, then washing to neutral pH, drying, treating with 1Msulfuric acid at room temperature for about 45 mins, then washing toneutral pH, and air drying.

To make the cellulose dissolution dope, the activated cellulose samplewas incorporated into Lithium Chloride (8% w/v)/N, N-dimethylacetamidewith Lauryl gallate (10% w/w versus added cellulose sample) and mucicacid (5% w/w versus added cellulose sample) as the additives, stirringat 120° C. to 130° C. for about 90 mins, cooling down, thencentrifugation at 2500 rpm for about 60 mins to remove the undissolvedimpurities and to make the dissolution cellulose dope in a solidconcentration about 4% to 6%. Then the cellulose dope was used toproduce continuous regenerated cellulose filament and textile products,as set forth in the schematic of FIG. 6.

The physical properties of the regenerated cellulose monofilament weremeasured. The monofilament had a tenacity ranging from 1.3 g/den to 1.8g/den and a strain at break of about 10% to 12%.

Optical microscopy images were taken of the produced regeneratedcellulose filaments. Particularly, FIG. 7a illustrates microscopy images(4×) of a single regenerated cellulose filament. FIG. 7b is across-sectional microscopy image (4×) of a bundle filament, wherein thecross-section of each individual filament indicates an oval-alike shape.FIG. 7c is a confocal microscopy image (2×) of a knitting sample,depicting multi-filaments.

Example 11 The Physical Properties of Regenerated Polyester Producedfrom Recycling Polycotton Textiles

Polycotton textiles were subjected to the subcritical water treatment(condition II) described in Example 6, and then the dissolved TPA wasrecovered by precipitation using a pH adjustment (e.g. pH 2-pH 4). Theprecipitated TPA was then carried forward to crystallization. Thisentailed heating an aqueous solution with precipitated TPA to atemperature of about 250° C. to 300° C., a ratio of solid:water of about1:5, with a residence time of about 5 minutes. The crystalized TPA wasthen treated with ethylene glycol in batch autoclave at temperaturesabout 290° C. with Antimony metal (Sb₂O₃) as catalyst for a PETpolymerization process to produce regenerated PET with a targetintrinsic viscosity (IV) of 0.620 dl/g.

FT-IR (Jasco 6200 with Pike MIRacle ATR attachment. Range: 4000-600cm⁻¹, Number of scans: 128) testing was conducted to analyze the TPAproduced during the TPA precipitation step, as shown in FIG. 8.

NMR analysis of the crystallized TPA from water recrystallization isshown in FIG. 9a . Precipitated TPA powder from the polycotton fabrics(zoomed at the aliphatic region) is shown before (FIG. 9b ) and afterrecrystallization (FIG. 9c ). As shown, after recrystallization, areduction in impurities was observed.

The Differential Scanning calorimetry (DSC) of regenerated PET chipproduced from 100% recycled TPA is shown in FIG. 10a . DSC analysis wasperformed using a TA Instruments Discovery Model DSC utilizing a“heat-cool-heat” method to remove any thermal history based onprocessing history. The second heating scan was performed from (either 0or −90° C.) to 325° C. at a rate of 10° C. As shown, The PET referencestandard peak temperature is 246.139° C., and the disclosed methodproduced regenerated PET with a peak temperature is 251.800° C.

The thermogravimetric analysis (TGA) of regenerated PET chip producedfrom 100% recycled TPA is shown in FIG. 10b . TGA analysis was performedusing a TA instruments Discovery Model TGA utilizing a temperature rampfrom room temperature to 700° C. at a rate of 20° C./min under nitrogenatmosphere. As shown, the PET reference standard onset x=425.33° C., andthe disclosed method produced regenerated PET with an onset x=426.040°C.

1.-20. (canceled)
 21. A method of producing terephthalic acid (TPA) froma polyester waste textile material, the method comprising: treating thepolyester waste textile material in a subcritical water reactor at atemperature of about 105° C. to 190° C., a pressure of about 40 to 300psi, or both for about 0 to 90 minutes, wherein a dissolved TPA andethylene glycol (EG) is produced, and wherein a regenerated polyethyleneterephthalate (PET) produced from the TPA has a peak temperature asmeasured by differential scanning calorimetry and an onset temperatureas measured by thermogravimetric analysis within +/−5% of that ofstandard reference PET.
 22. The method of claim 21, wherein theregenerated PET produced from the TPA has the onset temperature asmeasured by thermogravimetric analysis within +/−1% of that of standardreference PET.
 23. The method of claim 21, wherein the regenerated PETproduced from the TPA has the peak temperature as measured bydifferential scanning calorimetry within 2.3% of standard reference PETor the onset temperature as measured by thermogravimetric analysiswithin 0.2% of that of standard reference PET.
 24. The method of claim21, wherein the treating in the subcritical water reactor comprises a pHranging from about 10-14.
 25. The method of claim 21, wherein thetreating in the subcritical water reactor comprises about 5% (w/v)sodium hydroxide.
 26. The method of claim 21, wherein the polyesterwaste textile material/water ratio is about 1:5.
 27. The method of claim21, further comprising recovering the TPA.
 28. The method of claim 27,wherein the recovering the TPA is carried out using a pH adjustment ofabout pH 2-pH
 4. 29. The method of claim 28, further comprising treatingthe recovered TPA with ethylene glycol in a PET polymerization processto produce the regenerated PET.
 30. The method of claim 29, wherein thetreating comprises an autoclave at temperatures about 290° C. withAntimony metal (Sb₂O₃) as catalyst.
 31. The method of claim 29, whereinthe regenerated PET has an intrinsic viscosity of about 0.620 dl/g. 32.The method of claim 21, further comprising recovering the ethyleneglycol.
 33. The method of claim 32, wherein recovering the ethyleneglycol comprises vacuum distillation.
 34. The method of claim 21,further comprising recovering the TPA and recovering the ethyleneglycol.